<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        body {
            height: 100vh;
            display: flex;
            justify-content: center;
            align-items: center;
        }
        
        .search {
            width: 175px;
            height: 150px;
        }
        
        .search .con {
            font-size: 20px;
            width: 100%;
            margin-bottom: 5px;
            border: 1px solid gray;
            box-shadow: 0px 3px 4px rgb(207, 207, 207);
            position: relative;
            /* display: none; */
        }
        
        .search .con::before {
            content: '';
            width: 0;
            height: 0;
            position: absolute;
            top: 28px;
            left: 18px;
            border: 8px solid #000;
            border-style: solid dashed dashed;
            border-color: rgb(93, 93, 93) transparent transparent;
        }
    </style>
</head>

<body>
    <div class="search">
        <div class="con">123</div>
        <input type="text" placeholder="请输入您的快递单号" class="jd">
    </div>
    <script>
        var con = document.querySelector('.con');
        var jd_input = document.querySelector('.jd');
        jd_input.addEventListener('keyup', function(e) {
            // console.log('输入内容');
            if (this.value == '') {
                con.style.display = 'none';
            } else {
                con.style.display = 'block';
                con.innerText = this.value;
            }
        })

        // 失去焦点隐藏 con盒子
        jd_input.addEventListener('blur', function() {
            con.style.display = 'none';
        });
        jd_input.addEventListener('focus', function() {
            if (this.value !== '') {
                con.style.display = 'block';
            }
        });
    </script>
</body>

</html>